The present invention relates to a working position measuring system for projecting a laser beam by rotary irradiation and for measuring a working position from photodetecting condition of the laser beam.
In the past, as a typical device for forming a reference plane by projecting a laser beam by rotary irradiation, a rotary laser device and a photodetection device for receiving the laser beam have been known.
The rotary laser device forms a reference plane by irradiating and rotating a laser beam with a spot-like luminous flux. For instance, by irradiating and rotating the laser beam within a horizontal plane, a horizontal reference plane can be formed. By irradiating and rotating the laser beam within a vertical plane, a vertical reference plane can be formed. By irradiating and rotating the laser beam within a tilted plane, a tilted reference plane can be formed.
The photodetection device comprises a photodetection unit for receiving and detecting the laser beam. Based on the laser beam detected by the photodetection unit, measurement is made to determine a horizontal reference position, a vertical reference position, etc.
When a conventional type working position measuring system is used in a relatively narrow space such as in a room, the photodetection device with the smaller photodetection unit is used. In order that the photodetection unit can receive the laser beam, an operator must move the photodetection device in an upward or downward direction, for instance, and a position of the photodetection device must be aligned so that the photodetection unit can receive the laser beam.
When the working position measuring system is used in a wide outdoor space for civil engineering work by using a construction machine, a range for positioning of the photodetection device with respect to the reference plane is also widened. If the photodetection unit is small, it is difficult to operate manually by the operator, and the photodetection unit is designed in larger size. For instance, when the reference plane to be formed is a horizontal reference plane, the photodetection device is equipped with a photodetection unit of several tens of cm in length in an up-to-bottom direction, and, in some cases, of more than 1 m in length.
In the construction machine represented by a bulldozer, operation control in a plane is performed by a combination operation of the rotary laser device and the photodetection device installed on the construction machine. When the operating condition of the construction machine is to be controlled, a GPS position measuring device is added in some cases, and 3 dimensional operation control is carried out using three from ground positions and elevation. By the GPS position measuring device, a position in a horizontal direction on the ground surface is detected. To detect the direction of elevation, the stable rotary laser device and the photodetection device are used.
FIG. 16 shows a rotary laser device 1 used mostly in indoor operation and a photodetection device 2 for detecting a laser beam 3 projected from the rotary laser device 1.
The photodetection device 2 is arranged, for instance, on a wall (not shown) in an area where the laser beam 3 can reach. Reference numeral 4 denotes a reference line formed by the laser beam 3, and 5 represents a setting reference line to be set at a position deviated from the reference line 4 by a predetermined distance.
FIG. 17 shows the photodetection device 2 to be used in indoor operation. The photodetection device 2 comprises a photodetection unit 6, a display unit 7 with an index for indicating whether a scanning position is at the center or above or under the center when the laser beam 3 passes through the photodetection unit 6, a buzzer 8 for issuing an alarm when the laser beam 3 concurs with the center of the photodetection unit 6, and switches 9 and 10 for switching over the setting of the display unit 7 and the buzzer 8. An index line 12 for indication is marked at a position corresponding to the height at the center of the photodetection unit 6 on the photodetection device 2.
The photodetection unit 6 is designed in rectangular shape with longer side in a vertical direction. The photodetection unit 6 has a pair of photodetection elements 13 and 14 each in form of a right-angle triangle and these two elements are divided by a diagonal line, and the index line 12 is set so as to pass through the center of the photodetection unit 6. A photodetection area of each of the photodetection elements 13 and 14 varies according to the change of the scanning position of the laser beam 3. When the laser beam 3 to form the reference plane passes through the two photodetection elements 13 and 14, each of the photodetection elements 13 and 14 produces an output, which is proportional to a ratio between the areas where the laser beam 3 is projected. A position of the reference line 4 is obtained based on this output, and the setting reference line 5 is marked at a position deviated from the reference line 4 by a predetermined distance.
Next, FIG. 18 shows the rotary laser device 1 and a photodetection device 15 when these are used on a construction machine.
The rotary laser device 1 is fixed on a tripod 16 installed at a predetermined position K, and a reference plane is formed by the laser beam 3 projected from the rotary laser device 1. The photodetection device 15 is fixed on a mounting pole 19 erected on a working tool of the construction machine, e.g. on a blade 18 of a bulldozer 17. When a distance from a ground surface at the predetermined position K to the reference plane is already known and a distance from a reference position of a photodetection unit (not shown) of the photodetection device 15 to a position of an edge 18a of the blade 18 is also already known, ground leveling operation can be carried out as per a planned plane if the development operation is performed in such manner that a photodetection position (light receiving position) of the laser beam 3 on the photodetection unit is maintained at a predetermined position.
FIG. 19 represents the photodetection device 15 to be used primarily on a construction machine.
The photodetection device 15 is fixed on the mounting pole 19 by means of pole clamps 21. A pair of photodetection units 23 (only one of them is shown) is installed on both sides of a main unit 22 of the photodetection device 15. A storage battery receiving unit 24 is arranged at a bottom of the main unit 22. The photodetection unit 23 comprises a multiple of photodetection sensors 25 arranged in a longitudinal direction. By identifying the photodetection sensor 25 receiving the laser beam 3 among the photodetection sensors 25, a photodetecting position of the laser beam 3 can be detected.
Although not shown in the figure particularly, a GPS position measuring device is installed on the construction machine, e.g. the bulldozer 17. An absolute position of the working point can be detected by the GPS position measuring device. By combining the operating position with the operating information at the operating position, 3-dimensional operation can be carried out.
In the photodetection device 2 used in indoor operation, the photodetection unit 6 is very small and of several cm in length. Unless the laser beam 3 is projected within the photodetection range of the photodetection unit 6, the reference position cannot be detected.
When a ground surface is excavated or the ground is filled with soil at a working place in accordance with the reference plane by using a construction machine, e.g. a bulldozer, ground leveling operation must be carried out in many cases on the topographical condition beyond the photodetection range of the photodetection unit 23. In the photodetection device with photodetection range of several tens of cm, photodetection or light receiving is difficult to achieve.
Further, when the GPS position measuring device is used and 3-dimensional operation with difference in height is controlled corresponding to operation zones, the photodetection range of the photodetection unit 23 must cover the changes in height of the working plane in addition to the topographical change. In this type of work, the vertical change of the reference plane crossing the photodetection unit 23 of the photodetection device 15 results in the change of excavating operation in the range of several tens of cm to nearly 1 m.
The blade 18 is moved up and down to cope with the topography, and the photodetection device 15 installed on the blade 18 may not be adequate even when the photodetection device 15 has the photodetection unit 23 of 300 mm in length, for instance. Therefore, in order to widen the photodetection range of the photodetection unit 23, it is designed sometimes in such manner that the mounting pole 19 is made longer or shorter to move the photodetection device 15 itself up or down.
However, problem arises in that the photodetection unit 23 with long length must have a multiple of the short photodetection elements 25 and is very expensive. Also, the device to move the photodetection unit 23 up and down must be designed in complicated structure including a driving unit and a control unit for the driving unit, and the device is very costly.